Combined evaluation of oscillatory rheometry and isothermal calorimetry for the monitoring of hardening stage of Portland cement compositions blended with bauxite residue from Bayer process generated in different sites in Brazil

Abstract Bauxite residue (BR), a by-product of alumina and aluminum production, consists of high aluminum, silica, and iron content, and sodium from the bauxite ore digestion during the Bayer process. This waste is still being disposal into the lakes of mud, causing some environmental problems. So, the search for its application has gained interest. Studies reported in literature point out that one of the most promising applications is in association with Portland cement, which can also help to reduce the environmental impact caused by the CO2-emissions in its production. In this work, a combined evaluation of oscillatory rheometry and isothermal calorimetry was performed for the monitoring of the hardening stage of Portland cement (PC) compositions blended with BR generated in different sites in Brazil. The time-sweep test was applied to obtain the consistency gain of suspensions over-time, allowing us to understand the physical parameters of consolidation, while the changes in the hydration reaction showed considerable differences in the chemical contribution. As a conclusion, it was clear the impact of each BR, mainly due to the aspects related to soluble aluminates, silicates, and sodium, which in association with the soluble ions from PC, affected the chemical reaction and agglomeration/flocculation forces of particles.

Download Full-text

The impact of lithium nitrate on the physical and mechanical properties of Portland cement)

MATEC Web of Conferences ◽

10.1051/matecconf/201816304002 ◽

2018 ◽

Vol 163 ◽

pp. 04002

Author(s):

Justyna Zapała-Sławeta ◽

Zdzisława Owsiak

Keyword(s):

Mechanical Properties ◽

Compressive Strength ◽

Portland Cement ◽

Isothermal Calorimetry ◽

Setting Time ◽

Physical And Mechanical Properties ◽

Strength Development ◽

Lithium Nitrate ◽

Early Hydration ◽

The Impact

The effectiveness of lithium nitrate as a chemical additive which reduces the negative effects of alkali aggregate reaction was subject to research by scientists in many centres around the world. The literature data on the impact of lithium nitrate on the physical and mechanical properties of cements are rare. Without a precise definition of the impact of lithium nitrate on the cement properties, it is extremely hard to determine its real advantages in practical usage. In this paper, studies were undertaken to assess the impact of LiNO3 on the properties of pastes and mortars with Portland cement. The rate of hydration of the cement with lithium additive was examined by isothermal calorimetry, measurements of setting time and phase composition of cement pastes in the initial stages of hydration. The influence of the admixture on the compressive strength development of mortars after 2, 7 and 28 days of hardening was also researched. Results indicate that lithium nitrate accelerates the early hydration of Portland cement, affecting the precipitation of hydration products. The compressive strength of mortars with lithium admixture decrease after 28 days, although 2 an 7-day strength were greater than the control mortars.

Download Full-text

Influence of organosilicon admixtures on the hydration of Portland cement

Journal of Thermal Analysis and Calorimetry ◽

10.1007/s10973-021-10978-x ◽

2021 ◽

Author(s):

Kalina Grabowska ◽

Marcin Koniorczyk

Keyword(s):

Activation Energy ◽

Portland Cement ◽

Cement Hydration ◽

Isothermal Calorimetry ◽

Reference Sample ◽

Bound Water ◽

Cement Matrix ◽

Tg Analysis ◽

The Impact ◽

Portland Cement Hydration

AbstractThe impact of three different organosilicon compounds: poly(dimethylsiloxane) (PDMS), potassium methylsiliconate (MESI) and triethoxyoctylsilane (OTES), used as integral admixtures, on Portland cement hydration has been investigated by isothermal calorimetry and DTA-TG analysis. The silicon-based compounds are widely used as internal hydrophobic agents added into batch water; therefore, their effectiveness was investigated by means of capillary water absorption test. The isothermal calorimetry was used to measure the rate and amount of heat released during ordinary Portland cement hydration with integral organosilicon admixtures at 20 °C, 30 °C, 40 °C and 50 °C. It allowed to determine the activation energy as well. The results indicate that used admixtures (except MESI admixture) decrease in the rate and amount of heat release during cement hydration. In addition, it is noticeable that the addition of MESI admixture significantly prolongs the induction period and delays hydration. In contrast to MESI and OTES admixtures, PDMS-based admixture does not affect significant on the activation energy. DTA-TG analysis had shown differences between reference sample and samples containing organosilicon admixtures during thermal decomposition, in terms of the amount of moisture and bound water, as well as Ca(OH)2 or carbonates. The results presented in this paper enable a better understanding of the interactions between the organosilicon integral admixtures and the cement matrix. The study shows the effect of integral admixtures on cement hydration and thus the potential effect on the final properties of the cement-based material.

Download Full-text

Experience in the use of double broncholytic therapy in occupational practice

Russian Journal of Occupational Health and Industrial Ecology ◽

10.31089/1026-9428-2019-59-5-303-307 ◽

2019 ◽

pp. 303-307

Author(s):

Elena A. Beigel ◽

Natalya G. Kuptsova ◽

Elena V. Katamanova ◽

Oksana V. Ushakova ◽

Oleg L. Lakhman

Keyword(s):

Quality Of Life ◽

Personal Data ◽

The Body ◽

Step Test ◽

Aluminum Production ◽

Chronic Obstructive ◽

Body Plethysmography ◽

Occupational Copd ◽

The Impact

Introduction. Occupational chronic obstructive pulmonary disease (COPD) is one of the leading nosological forms of occupational respiratory disease. Numerous studies have shown high effectiveness of the combination of indacaterol/glycopyrronium (Ultibro®breezhaler®) on the impact on clinical and functional indicators in the treatment of COPD in General practice.The aim of the investigation the case of occupational COPD with the analysis of the dynamics of functional indicators, tolerance to physical load and evaluation of the quality of life of workers engaged in aluminum production by using combination of indacaterol/glycopyrronium.Materials and methods. The random sampling method included 20 men, workers of aluminum production, with the established diagnosis of professional COPD at the age of 40 to 60 years. The survey was conducted (Borg scale, medical Research Council scale (mMRC) and COPD Assessment Test (CAT). Functional methods of studies were conducted: spirometry, body plethysmography, electrocardiography (ECG) and the six-minute stepper test (6-MST).Results. Against the background of 8 weeks of therapy, the volume of forced exhalation for 1 minute (FEV1) increased by 14.7% and amounted to 67.90% of the due values, the forced vital capacity of the lungs (FVC) increased by 11.3% and amounted to 76.95% of the due. According to the body plethysmography (BPG) is set to decrease in residual lung volume on average by 13.4% and static hyperinflation, confirmed by the decrease in functional residual volume (FRV) of 18.8%. During the study period increased physical activity of patients. The average difference between the distance traveled in the six-minute step test before and after treatment was 58.8 m. The analysis of personal data showed that the quality of life of patients improved, the total score in the questionnaire CAT at the beginning of the study was 16.9 points, and after 8 weeks decreased by 63% and amounted to 10.7 points.Conclusions: The Results indicate a positive effect of combination therapy with indacaterol/glycopyrronium on the course and progression of occupational COPD.

Download Full-text

Damage Evolution of Granodiorite after Heating and Cooling Treatments

Minerals ◽

10.3390/min11070779 ◽

2021 ◽

Vol 11 (7) ◽

pp. 779

Author(s):

Mohamed Gomah ◽

Guichen Li ◽

Salah Bader ◽

Mohamed Elkarmoty ◽

Mohamed Ismael

Keyword(s):

Mechanical Properties ◽

Tensile Strength ◽

Failure Mode ◽

Physical And Mechanical Properties ◽

P Wave ◽

Physical Parameters ◽

Slow Cooling ◽

Heating And Cooling ◽

Natural Rock ◽

The Impact

The awareness of the impact of high temperatures on rock properties is essential to the design of deep geotechnical applications. The purpose of this research is to assess the influence of heating and cooling treatments on the physical and mechanical properties of Egyptian granodiorite as a degrading factor. The samples were heated to various temperatures (200, 400, 600, and 800 °C) and then cooled at different rates, either slowly cooled in the oven and air or quickly cooled in water. The porosity, water absorption, P-wave velocity, tensile strength, failure mode, and associated microstructural alterations due to thermal effect have been studied. The study revealed that the granodiorite has a slight drop in tensile strength, up to 400 °C, for slow cooling routes and that most of the physical attributes are comparable to natural rock. Despite this, granodiorite thermal deterioration is substantially higher for quick cooling than for slow cooling. Between 400:600 °C is ‘the transitional stage’, where the physical and mechanical characteristics degraded exponentially for all cooling pathways. Independent of the cooling method, the granodiorite showed a ductile failure mode associated with reduced peak tensile strengths. Additionally, the microstructure altered from predominantly intergranular cracking to more trans-granular cracking at 600 °C. The integrity of the granodiorite structure was compromised at 800 °C, the physical parameters deteriorated, and the rock tensile strength was negligible. In this research, the temperatures of 400, 600, and 800 °C were remarked to be typical of three divergent phases of granodiorite mechanical and physical properties evolution. Furthermore, 400 °C could be considered as the threshold limit for Egyptian granodiorite physical and mechanical properties for typical thermal underground applications.

Download Full-text

A Review of Photocatalytic Materials for Urban NOx Remediation

Catalysts ◽

10.3390/catal11060675 ◽

2021 ◽

Vol 11 (6) ◽

pp. 675

Author(s):

Hugo Savill Russell ◽

Louise Bøge Frederickson ◽

Ole Hertel ◽

Thomas Ellermann ◽

Steen Solvang Jensen

Keyword(s):

Photocatalytic Oxidation ◽

Urban Air Pollution ◽

Field Trials ◽

Urban Environments ◽

Physical Parameters ◽

Nox Removal ◽

Removal Efficiencies ◽

The Impact ◽

By Products ◽

Photocatalytic Materials

NOx is a pervasive pollutant in urban environments. This review assesses the current state of the art of photocatalytic oxidation materials, designed for the abatement of nitrogen oxides (NOx) in the urban environment, and typically, but not exclusively based on titanium dioxide (TiO2). Field trials with existing commercial materials, such as paints, asphalt and concrete, in a range of environments including street canyons, car parks, tunnels, highways and open streets, are considered in-depth. Lab studies containing the most recent developments in the photocatalytic materials are also summarised, as well as studies investigating the impact of physical parameters on their efficiency. It is concluded that this technology may be useful as a part of the measures used to lower urban air pollution levels, yielding ∼2% NOx removal in the immediate area around the surface, for optimised TiO2, in some cases, but is not capable of the reported high NOx removal efficiencies >20% in outdoor urban environments, and can in some cases lower air quality by releasing hazardous by-products. However, research into new material is ongoing. The reason for the mixed results in the studies reviewed, and massive range of removal efficiencies reported (from negligible and up to >80%) is mainly the large range of testing practices used. Before deployment in individual environments site-specific testing should be performed, and new standards for lab and field testing should be developed. The longevity of the materials and their potential for producing hazardous by-products should also be considered.

Download Full-text

Modelling H2 and its effects on star formation using a joint implementation of gadget-3 and KROME

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stab1015 ◽

2021 ◽

Vol 504 (2) ◽

pp. 2325-2345

Author(s):

Emanuel Sillero ◽

Patricia B Tissera ◽

Diego G Lambas ◽

Stefano Bovino ◽

Dominik R Schleicher ◽

...

Keyword(s):

Star Formation ◽

Formation Rate ◽

Physical Parameters ◽

Density Profiles ◽

Star Forming ◽

Chemical Enrichment ◽

Numerical Resolution ◽

Stellar Radiation ◽

Wide Range ◽

The Impact

ABSTRACT We present p-gadget3-k, an updated version of gadget-3, that incorporates the chemistry package krome. p-gadget3-k follows the hydrodynamical and chemical evolution of cosmic structures, incorporating the chemistry and cooling of H2 and metal cooling in non-equilibrium. We performed different runs of the same ICs to assess the impact of various physical parameters and prescriptions, namely gas metallicity, molecular hydrogen formation on dust, star formation recipes including or not H2 dependence, and the effects of numerical resolution. We find that the characteristics of the simulated systems, both globally and at kpc-scales, are in good agreement with several observable properties of molecular gas in star-forming galaxies. The surface density profiles of star formation rate (SFR) and H2 are found to vary with the clumping factor and resolution. In agreement with previous results, the chemical enrichment of the gas component is found to be a key ingredient to model the formation and distribution of H2 as a function of gas density and temperature. A star formation algorithm that takes into account the H2 fraction together with a treatment for the local stellar radiation field improves the agreement with observed H2 abundances over a wide range of gas densities and with the molecular Kennicutt–Schmidt law, implying a more realistic modelling of the star formation process.

Download Full-text

Stiffness and Strength of Stabilized Organic Soils—Part I/II: Experimental Database and Statistical Description for Machine Learning Modelling

Geosciences ◽

10.3390/geosciences11060243 ◽

2021 ◽

Vol 11 (6) ◽

pp. 243

Author(s):

Hernandez-Martinez Francisco G. ◽

Al-Tabbaa Abir ◽

Medina-Cetina Zenon ◽

Yousefpour Negin

Keyword(s):

Machine Learning ◽

Statistical Analysis ◽

Portland Cement ◽

Soil Stabilization ◽

Data Availability ◽

Data Repository ◽

Organic Soils ◽

Experimental Database ◽

Soil Mixing ◽

The Impact

This paper presents the experimental database and corresponding statistical analysis (Part I), which serves as a basis to perform the corresponding parametric analysis and machine learning modelling (Part II) of a comprehensive study on organic soil strength and stiffness, stabilized via the wet soil mixing method. The experimental database includes unconfined compression tests performed under laboratory-controlled conditions to investigate the impact of soil type, the soil’s organic content, the soil’s initial natural water content, binder type, binder quantity, grout to soil ratio, water to binder ratio, curing time, temperature, curing relative humidity and carbon dioxide content on the stabilized organic specimens’ stiffness and strength. A descriptive statistical analysis complements the description of the experimental database, along with a qualitative study on the stabilization hydration process via scanning electron microscopy images. Results confirmed findings on the use of Portland cement alone and a mix of Portland cement with ground granulated blast furnace slag as suitable binders for soil stabilization. Findings on mixes including lime and magnesium oxide cements demonstrated minimal stabilization. Specimen size affected stiffness, but not the strength for mixes of peat and Portland cement. The experimental database, along with all produced data analyses, are available at the Texas Data Repository as indicated in the Data Availability Statement below, to allow for data reproducibility and promote the use of artificial intelligence and machine learning competing modelling techniques as the ones presented in Part II of this paper.

Download Full-text

The Impact of Traffic-Induced Bridge Vibration on Rapid Repairing High-Performance Concrete for Bridge Deck Pavement Repairs

Advances in Materials Science and Engineering ◽

10.1155/2014/632051 ◽

2014 ◽

Vol 2014 ◽

pp. 1-9 ◽

Cited By ~ 5

Author(s):

Wei Wang ◽

Shuo Liu ◽

Qizhi Wang ◽

Wei Yuan ◽

Mingzhang Chen ◽

...

Keyword(s):

Compressive Strength ◽

High Performance ◽

Bridge Deck ◽

High Performance Concrete ◽

Reduction Rate ◽

Harmonic Vibration ◽

Hydration Reaction ◽

Self Healing ◽

The Impact ◽

Bridge Deck Pavement

Based on forced vibration tests for high-performance concrete (HPC), the influence of bridge vibration induced by traveling vehicle on compressive strength and durability of HPC has been studied. It is concluded that 1 d and 2 d compressive strength of HPC decreased significantly, and the maximum reduction rate is 9.1%, while 28 d compressive strength of HPC had a slight lower with a 3% maximal drop under the action of two simple harmonic vibrations with 2 Hz, 3 mm amplitude, and 4 Hz, 3 mm amplitude. Moreover, the vibration had a slight effect on the compressive strength of HPC when the simple harmonic vibration had 4 Hz and 1 mm amplitude; it is indicated that the amplitude exerts a more prominent influence on the earlier compressive strength with the comparison of the frequency. In addition, the impact of simple harmonic vibration on durability of HPC can be ignored; this shows the self-healing function of concrete resulting from later hydration reaction. Thus, the research achievements mentioned above can contribute to learning the laws by which bridge vibration affects the properties of concrete and provide technical support for the design and construction of the bridge deck pavement maintenance.

Download Full-text

The influence of physical parameters on the in-situ metal carbonyl complex formation studied with the Fast On-line Reaction Apparatus (FORA)

Radiochimica Acta ◽

10.1515/ract-2020-0035 ◽

2021 ◽

Vol 109 (4) ◽

pp. 261-281

Author(s):

Yves Wittwer ◽

Robert Eichler ◽

Dominik Herrmann ◽

Andreas Türler

Keyword(s):

Gas Flow ◽

Metal Carbonyl ◽

Fission Products ◽

Reaction Chamber ◽

Single Atom ◽

Physical Parameters ◽

Carbonyl Complex ◽

Reaction Conditions ◽

On Line ◽

The Impact

Abstract The Fast On-line Reaction Apparatus (FORA) was used to investigate the influence of various reaction parameters onto the formation and transport of metal carbonyl complexes (MCCs) under single-atom chemistry conditions. FORA is based on a 252Cf-source producing short-lived Mo, Tc, Ru and Rh isotopes. Those are recoiling from the spontaneous fission source into a reaction chamber flushed with a gas-mixture containing CO. Upon contact with CO, fission products form volatile MCCs which are further transported by the gas stream to the detection setup, consisting of a charcoal trap mounted in front of a HPGe γ-detector. Depending on the reaction conditions, MCCs are formed and transported with different efficiencies. Using this setup, the impact of varying physical parameters like gas flow, gas pressure, kinetic energy of fission products upon entering the reaction chamber and temperature of the reaction chamber on the formation and transport yields of MCCs was investigated. Using a setup similar to FORA called Miss Piggy, various gas mixtures of CO with a selection of noble gases, as well as N2 and H2, were investigated with respect to their effect onto MCC formation and transport. Based on this measurements, optimized reaction conditions to maximize the synthesis and transport of MCCs are suggested. Explanations for the observed results supported by simulations are suggested as well.

Download Full-text

Basic Physical and Mechanical Properties of Composites Based on Three Different Cements

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.677.186 ◽

2016 ◽

Vol 677 ◽

pp. 186-190 ◽

Cited By ~ 1

Author(s):

Monika Čáchová ◽

Eva Vejmelková ◽

Kateřina Šestáková ◽

Pavel Reiterman ◽

Martin Keppert ◽

...

Keyword(s):

Mechanical Properties ◽

Portland Cement ◽

Open Porosity ◽

Mercury Porosimetry ◽

Physical And Mechanical Properties ◽

Mineralogical Composition ◽

Physical Parameters ◽

Vacuum Saturation ◽

Saturation Method ◽

Properties Of Composites

This article is focused on cement based composites. Two cements differing in mineralogical composition are utilised as main binder in composites mixtures. Results of measured physical parameters of studied materials are presented. For the sake of comparison, a reference material with Portland cement was also prepared. Basic physical properties (measured by water vacuum saturation method and by helium pycnometry), characterizations of pore system (determined by mercury porosimetry) and mechanical properties are the matter of this study. Composites show various open porosity; the results of open porosity of materials containing special cements show higher values, in comparison with composite based on Portland cement. This fact of course influences other material characteristics - mainly mechanical properties.

Download Full-text